Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Deferred tax assets
Net operating loss carryforwards	$ 75,492	$ 66,265
Capitalized research and development expenses	4,451	6,185
Stock-based compensation	1,590	1,604
Accrued expenses and other	1,160	1,193
Lease liability	486	478
Research and development credits	1,038	830
Inventory reserve	295	432
Interest expense carryforward	1,620	691
Gross deferred tax asset before valuation allowance	86,132	77,678
Less: valuation allowance	(85,523)	(76,782)
Total deferred tax asset	609	896
Deferred tax liabilities
Depreciation and amortization	(244)	(326)
Right of use asset	(365)	(430)
Gross deferred tax liability	(609)	(756)
Less: valuation allowance	(85,523)	(76,782)
Net deferred tax asset	$ 0	$ 140